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Finding Planes with Satellites

127 planes were reported in the past few days as people helped search Blackbridge imagery for missing flight MH370 — out of more than thousand reports overall. While none of these finds pointed to the plane in question, most were airliners captured by satellites mid air, looking like a series of colored ghost images:

This characteristic pattern of ghost images stems from push-broom cameras used by many earth observing satellites. Images of such cameras are composed of single-row arrays of pixel sensors on the focal plane that scan the earth as the satellite orbits at 7.5 kilometers per second ( 4.7 miles per second ) — just like a scanner over a document. Each sensor row captures one color at a time. In this setup, objects that move fast leave ghost images in different colors, since their position underneath the satellite changes from one row to the next.

In BlackBridge satellites, these sensor rows are packed into two CCD array units. Blue and green sit next to each other in one array, and red and infrared bands in another. This is why the red ghost appears further out when using red, green and blue channels as in the imagery here.